The hearing scheduled for Wednesday comes after the measure ran into opposition during an Assembly hearing last year.
Supporters say the goal is to make sure underage drinkers aren't afraid to report a sexual assault or other violent crime or to seek emergency medical help just because they are breaking the law themselves by consuming alcohol.
But police say they are leery of restrictions on enforcement efforts.
The bill has bipartisan support in the Legislature and is sponsored by Democratic Sen. Fred Risser. His Senate district includes the University of Wisconsin-Madison campus.